1. Field of the Invention
The present invention relates to a sheet processing apparatus, and more specifically to a sheet processing apparatus having a feeding structure which improves the stability of sheet feeding.
2. The Related Art
Please refer to FIG. 1, a conventional sheet processing apparatus 100′ comprises a sheet-separating unit 1′ which includes a separating roller 11′ and a first driving device 12′, a sensor 2′, a convey unit 3′, a sheet-processing unit 4′, a discharge unit 5′, a second driving device 7′ and a system controller 8′. The separating roller 11′ is commanded by the first driving device 12′ to rotate counterclockwise for separating and feeding a sheet (not shown). The convey unit 3′ has a convey roller 31′, a convey pulley 32′ disposed against the convey roller 31′, with a convey path 6′ defined therebetween, a swingable arm 33′ and a driving device 34′. The swingable arm 33′ has one free end pivoted to the convey pulley 32′, and the other free end connected to the driving device 34′, thereby forcing the convey pulley 32′ to move with respect to the convey roller 31′ under the drive of the driving device 34′. Herein, the swingable arm 33′ has a middle portion pivoted to a housing (not shown). The sheet-processing unit 4′ is capable of scanning, printing and copying a plurality of sheets.
Take scanning the sheet for example, when the sheet processing apparatus 100′ is in work, the plural sheets are disposed at an original end of the separating roller 11′. The separating roller 11′ is urged by the first driving device 12′ to rotate for feeding one sheet downstream along the convey path 6′. The sensor 2′ detects a front end of the sheet and sends a signal to the system controller 8′. The second driving device 7′ is accordingly commanded by the system controller 8′ to operate the convey roller 31′ and the discharge unit 5′ to rotate. Consequently, the sheet will be conveyed downstream successively by the rotated convey roller 31′ to process by the sheet-processing unit 4′. When the front end of the sheet reaches the discharge unit 5′, a rear end of the sheet is still restrained between the convey roller 31′ and the convey pulley 32′. At this time, the system controller 8′ controls the driving device 34′ to make the swingable arm 33′ to swing so that the convey pulley 32′ is moved away from the convey roller 31′ with a small distance, releasing the conveying sheet. Thus the sheet will be conveyed only by the discharge unit 5′, avoiding pulling and dragging the sheet.
However, since the sheet processing apparatus 100′ provides with the swingable arm 33′, served as a transitional element, for forcing the convey pulley 32′ to butt against and separate the sheets from the convey roller 31′, the assembling inaccuracy and the attrition of the swingable arm 33′ is possible and apt to affect the engagement between the convey roller 31′ and the convey pulley 32′, as a result, having bad influence on the conveying stability for sheets.